Ethylene glycol and propylene glycol water solutions are popular heat transfer fluids due to the low corrosivity of the glycols and the low fire hazard associated with them. A problem with these solutions is their potential toxicity both to the environment and to food products or animals and the decrease in thermal conductivity of water solutions as the glycol concentration increases. Heat transfer solutions are often used in secondary refrigeration loops to transfer heat from a heat source to a source of cooling such as a compression refrigeration unit. A plethora of advantages can be had from using a secondary refrigeration loop rather than transporting the primary refrigerant to remote heat exchangers, which are in contact with a heat source.
A de-icer composition was disclosed in GB 1111936. The composition included urea, and an alkali metal or ammonium salt of a saturated carboxylic acid which contains up to 6 carbon atoms. U.S. Pat. No. 5,104,562 disclosed a coolant composition that comprised from about 3 to 9 parts by weight water, from about 1 to 2 parts by weight potassium formate, from about 1 to 9 parts by weigh of potassium acetate, from about 0 to 1.5 parts by weight urea, and from about 0 to 1.5 parts by weight of a glycol. U.S. Pat. No. 6,059,966 discloses a low-viscosity, aqueous coolant brine based on inhibited alkali metal acetates and/or formates having improved corrosion protection, wherein the coolant brines contain 0.2 to 5% by weight of alkali metal sulfites or pyrosulfites. WO9309198 disclosed a vapor absorbent composition comprising potassium formate for an absorbent refrigeration, air conditioning, heat pumping or dehumidifying system. WO9639472 disclosed a method for performing heat exchange transfer with a heat transfer medium and a heat exchange apparatus. The pumpable heat transfer medium for performing heat transfer with a target (b) was characterized in that it contains potassium formate dissolved in water. Canadian patent application 2,220,315 disclosed a composition comprising: (1) at least one potassium salt of a C1-9 carboxylic acid; and (2) a corrosion inhibitor package comprising: (a) sodium or potassium nitrite; (b) sodium borate pentahydrate; and (c) tolytriazole. EP 677 563 to Linde discloses a method of operating a refrigerating plant using an aqueous potassium formate solution as the refrigerant. WO 01/81497 assigned to Lubrizol Corp. was published Nov. 1, 2001 and taught potassium formate heat transfer fluids.
It would be desirable to identify a heat transfer fluid with lower toxicity than glycol solutions and desirably having better heat transfer properties and minimal tendency toward metal corrosion.